Conventional lock mechanism usually includes a first part mounted on one side of a door and a second part mounted on the other side of the door. During installation of the conventional lock mechanism, user generally uses a screw to connect the first and second parts on two different sides of the door such that the lock mechanism is fixed on the door. However, if any component in the first or second part is broken or requires to be replaced (e.g. cylinder), the user needs to disassemble the screw and then disassemble the first and second parts from the door in order to repair or replace the component. After repairing or replacing, the user also needs to mount the first and second parts on the door and then use the screw to connect the first and second parts. As a result, assembly/disassembly of the conventional lock mechanism is complex and inconvenient to the user.